In a small bowl whisk together the sour cream, 1/4 cup of the mayonnaise, and the horseradish.

In a large bowl, combine the crabmeat, the remaining 1/4 cup mayonnaise, 1/4 cup of the bread crumbs, the scallions, parsley, cayenne, salt and pepper, shape the crab mixture into eight patties with remaining 3/4 cup bread crumbs and pat off the excess.

In a large nonstick frying pan, heat the oil over moderate heat working in batches if necessary, fry the cakes until golden brown and crisp, about 2 minutes. Turn and fry until golden brown on the other side,about 2 minute longer. Drain on pepper towels. Serve with the horseradish cream.